Effects of surface stresses and voids on rayleigh waves in an elastic solid

Rayleigh waves propagating at the plane material boundary of an elastic half-space containing a distribution of voids (vacuous pores) are considered. It is found that the waves are generally dispersive and that the dispersion is caused by both the surface stresses exerted by the boundary and the voids inside. If the body is incompressible, voids have no influence on the motion. In the case of small frequency, the effect of the voids is just to modify the speed of propagation. If the frequency is small and surface stresses are due to a residual surface tension, there exists a critical wavelength at which waves propagate with the speed of pure shear waves and below which the motion is not possible. The critical wave length varies directly with the surface tension and the effect of the voids is to widen the range of wavelengths for which the waves exist.